/* Example showing how to enable debugging, and capture it into any
* custom logging system (syslog in this example, but any could be
* used). Note this uses the event API which is also available in
* non-C language bindings.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <syslog.h>
#include <guestfs.h>
static void message_callback (guestfs_h *g, void *opaque, uint64_t event, int event_handle, int flags, const char *buf, size_t buf_len, const uint64_t *array, size_t array_len);
/* Events we are interested in. This bitmask covers all trace and
* debug messages.
*/
static const uint64_t event_bitmask =
GUESTFS_EVENT_LIBRARY |
GUESTFS_EVENT_WARNING |
GUESTFS_EVENT_APPLIANCE |
GUESTFS_EVENT_TRACE;
int
main (int argc, char *argv[])
{
guestfs_h *g;
g = guestfs_create ();
if (g == NULL) {
perror ("failed to create libguestfs handle");
exit (EXIT_FAILURE);
}
/* By default, debugging information is printed on stderr. To
* capture it somewhere else you have to set up an event handler
* which will be called back as debug messages are generated. To do
* this use the event API.
*
* For more information see EVENTS in guestfs(3).
*/
if (guestfs_set_event_callback (g, message_callback,
event_bitmask, 0, NULL) == -1)
exit (EXIT_FAILURE);
/* This is how debugging is enabled:
*
* Setting the 'trace' flag in the handle means that each libguestfs
* call is logged (name, parameters, return). This flag is useful
* to see how libguestfs is being used by a program.
*
* Setting the 'verbose' flag enables a great deal of extra
* debugging throughout the system. This is useful if there is a
* libguestfs error which you don't understand.
*
* Note that you should set the flags early on after creating the
* handle. In particular if you set the verbose flag after launch
* then you won't see all messages.
*
* For more information see:
* http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs
*
* Error messages raised by APIs are *not* debugging information,
* and they are not affected by any of this. You may have to log
* them separately.
*/
guestfs_set_trace (g, 1);
guestfs_set_verbose (g, 1);
/* Do some operations which will generate plenty of trace and debug
* messages.
*/
if (guestfs_add_drive (g, "/dev/null") == -1)
exit (EXIT_FAILURE);
printf ("There is no output from this program. "
"Take a look in your system log file,\n"
"eg. /var/log/messages.\n");
if (guestfs_launch (g) == -1)
exit (EXIT_FAILURE);
guestfs_close (g);
exit (EXIT_SUCCESS);
}
/* This function is called back by libguestfs whenever a trace or
* debug message is generated.
*
* For the classes of events we have registered above, 'array' and
* 'array_len' will not be meaningful. Only 'buf' and 'buf_len' will
* be interesting and these will contain the trace or debug message.
*
* This example simply redirects these messages to syslog, but
* obviously you could do something more advanced here.
*/
static void
message_callback (guestfs_h *g, void *opaque,
uint64_t event, int event_handle,
int flags,
const char *buf, size_t buf_len,
const uint64_t *array, size_t array_len)
{
const int priority = LOG_USER|LOG_INFO;
char *event_name, *msg;
if (buf_len > 0) {
event_name = guestfs_event_to_string (event);
msg = strndup (buf, buf_len);
syslog (priority, "[%s] %s", event_name, msg);
free (msg);
free (event_name);
}
}